The invention relates to a method of using a container for a refrigerated fluid having an external container and an internal container, between which an evacuated intermediate space is situated which contains a superinsulating means, and wherein the superinsulating means is formed by several layers of foil provided with a metal layer, which foils are preferably separated from one another by spacers, preferably in the form of an insulating material, as well as to a corresponding container.
With respect to the state of the art, reference is made as an example to German Patent document DE 10 2005 014 479 A1 and also to the basically known electric synthetic foil capacitors (in the following, called foil capacitors). These are electric capacitors having insulating synthetic foils as a dielectric, in the case of which thin foils are equipped with the electrodes and are then joined as wraps or as individual layers for forming a capacitor (definition from “Wikipedia”).
A container, as indicated above, can be used as a tank for cryogenic hydrogen in a motor vehicle, which carries this hydrogen as fuel for preferably supplying the vehicle drive unit. Such future motor vehicles may also have a hybrid drive; i.e. can optionally or also additionally be driven by an electric motor, in which case an accumulator for electric energy is to be provided. However, electric energy is also used in a motor vehicle for supplying ancillary equipment and for this purpose also has to be stored in an appropriate fashion.
By way of the present invention, a particularly advantageous electric energy storage device was found for a vehicle that is equipped with a container as initially discussed above; i.e., with a container for a refrigerated fluid having an external container and an internal container, between which an evacuated intermediate space is situated which contains a superinsulator, and in which case the superinsulator is formed by several layers of foil provided with a metal layer, which foils are separated from one another by spacers, preferably in the form of an insulating material. Specifically, this container is therefore used as a storage device for electric energy in that the foils act as foil capacitor(s) and, for this purpose, are appropriately electrically contacted, so that an electric voltage can be applied to corresponding electric terminals on the exterior side of this container.
By means of the present invention, a particularly advantageous combination of functions is indicated in that the container for storing the fuel (in the form of cryogenic hydrogen) can simultaneously be used with relatively few changes or additional measures as a storage device for electric energy. Specifically, it was discovered that the foils, which are provided as a superinsulator in the container and which, in particular, are coated with a metal for forming a reflection layer, can simultaneously form a (basically known) foil capacitor.
In this case, the electric charge supplied by way of suitable electric terminals can be stored in the metallic coating of the foils. The foils will then operate as electrodes of the capacitor, while either the foils alone or the foil together with the spacers or the insulation layer and the vacuum between the internal container and external container act as the dielectric of the capacitor or of several individual capacitors formed by the plurality of foil layers. The individual capacitors are suitably connected together to form a sum capacitance which, in the present case, should also be included under the term “foil capacitor”. As far as the above-mentioned sum connection is concerned, this may be a series or a parallel connection. If, in this case, the foils are provided with a metallic layer only on one side—for reasons of weight and cost, preferably on an aluminum base-, the spacers or the insulating layer as well as the vacuum between mutually adjacent foils are necessarily a component of the dielectric of the capacitor. If both surfaces of the foil(s) are provided with a metal layer, depending on the electric interconnection of several foils, either only the electric foil itself or the foils together with the spacers or the insulation layers and the vacuum form the dielectric. Here, it is again pointed out that, in the known state of the art, the above-mentioned foils are, among other things, already metallically coated on one side for forming a reflection layer for heat radiation. In this context, the so-called biaxially oriented polyester films (“boPET”) should be mentioned, which are sold, for example, by the “Mylar” trade name and can be coated with aluminum by sputtering. According to “Wikipedia”, such films are currently already used in foil capacitors.
Although, in the case of the so-called cryotanks for passenger cars currently being produced in small series, approximately 50 to 70 foil layers are provided, so that the latter describe a total surface of approximately 100 square meters and therefore supply the thermal insulating space between the external container and the internal container by means of the present invention for an additional utilization as an electric energy storage device of a charging capacitance that should not be neglected, this capacitance or the electric capacitance of a foil capacitor according to the invention as a whole can be further increased particularly at a relatively low electric voltage if the foil(s) consist(s) of a semiconductor material. Polyacetylene or PTCDA (3,4,9,10 perylene tetra carboxylic acid dianhydride), for example, have such an electric semiconductor characteristic. By use of such materials, a quasi-formation of a pn-diode, a pin-diode or a Schottky diode then becomes possible, which each represent an electric capacitance.
Also for the purpose of an advantageous combination of functions, the electrical contacting of the metal layers of the foils can take place by way of the suspension structure of the internal container in the external container, in which case this suspension structure known to a person skilled in the art can either carry suitable electric conductors or can at least in sections itself, represent these conductors.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.